I think the problem is that DPRK is not going to stop trying to get a credible nuclear deterrent

And who can blame them? History contains at least one example of a leader who disarmed, and then at a later point got invaded by the US. One of the common properties of countries that have never been invaded by the US is the possession of nuclear weapons. DPRK rationally concludes that nuclear weapons can prevent any US invasion.

I won't enumerate the points here, but provide a link (https://nplusonemag.com/online-only/online-only/remote-diagnoses/).

Now China and Russia don't want North Korea to have nuclear weapons, that's for sure. Recent missile tests on a Chinese destroyer near North Korea seem aimed at reminding North Korea that its large neighbour is armed and potentially angry. But if even the mightiest country in the world (USA) cannot force the DPRK to abandon its nuclear ambitions, then I don't see how Russia or China can.

On a more positive note: so what if DPRK got nuclear-armed? Would it be rational for it to nuke another country? Kim Jong Un may act mad, but I think his moves show a ruthless, calculated rationality. Of course, none of the big UNSC countries would appreciate an upstart newcomer, but suppose the upstart succeeded, would the consequences really be nuclear war? Somehow I doubt it. The DPRK aren't stupid enough to actually _use_ a nuke. Like all weapons, the purpose of a nuke is in its threat of use, not its actual use.

China is nuclear-armed. It's never nuked anyone. Russia is nuclear-armed. It's never nuked anyone. UK, France, India... indeed, some even argue that China was able to economically open up and develop because its nuclear arsenal gave a 100% guarantee against any interventions by a jealous incumbent power acting to prevent it from taking first place. Ironically the presence of an non-precision uber-weapon ensures a kind of uneasy truce.